The present invention relates generally to actuators in a heating, ventilating, or air conditioning (HVAC) system and more particularly to HVAC actuators that use brushless direct current (BLDC) motors.
HVAC actuators are used to operate a wide variety of HVAC components such as air dampers, fluid valves, air handling units, and other components that are typically used in HVAC systems. For example, an actuator may be coupled to a damper in a HVAC system and may be used to drive the damper between an open position and a closed position. A HVAC actuator typically includes a motor and a drive device (e.g., a hub, a drive train, etc.) that is driven by the motor and coupled to the HVAC component.
Some HVAC actuators include mechanical end stops that define the ends of a range of movement of the drive device and/or the HVAC component. When the drive device encounters an unexpected end stop, the drive device and connected components may experience an impulse force that can cause premature breakage. For example, an unexpected end stop may occur when ice or other debris restricts the range of movement of the drive device and prevents it from reaching the expected end stop location. Existing solutions to this problem generally involve an operator recognizing that the drive device has unexpectedly stalled and initiating an automatic recalibration process to redefine the end stop locations. However, these solutions are unsatisfactory because they rely on the operator initiating the automatic calibration procedure in order to prevent damaging impulse forces at the mechanical end stops.